1. Field of the Invention
The present invention relates to a thermal gas-flow measuring instrument which measure flow rate of fluid to be measured with the use of a heating resistor and a temperature sensing resistor.
2. Description of the Related Art
Regarding instrument to measure flow rate of fluid to be measured based on the rate of heat transfer from a heating resistor to the fluid, there is a known technology disclosed in JP-B-5-16530(Patent Document 1). The flow detector described in Patent Document 1 has a first heating element detecting the flow velocity of the fluid, a second heating element surrounding the first heating element, and a fixed temperature difference control circuit which keeps the temperature difference between the first heating element and the second heating element at a specified value or zero. The second heating element is supported by a supporting member.
The technology described in Patent Document 1 uses the second heating resistor to suppress the occurrence of temperature drift by suppressing the heat releasing from the electrode lead wire connected to the first heating resistor to the support side.